1. Field of the Invention
The present invention relates generally to medical devices, kits, and methods. More particularly, the present invention relates to apparatuses and methods for removing tissue from tissue regions beneath a tissue surface.
The removal of diseased and other tissues is the basis for many surgical procedures and is accomplished in many different ways. Most commonly, the target tissue is excised using a cutting blade, such as a scalpel, in open surgical procedures. Typically, the cutting blade is advanced into a tissue through an exposed tissue surface, and the target tissue is simply cut out and removed. While very effective for tissue removal at or near an exposed tissue surface, this approach is less effective for tissue removal from sites spaced below the closest exposed tissue surface.
For removal of target tissue below a tissue surface, a surgeon can simply cut down to the level of the target tissue and cut out and remove the tissue at that level. The need to cut down through "non-target" tissue is, however, disadvantageous in several respects. First, surgically cutting through the overlying healthy tissue can create a much bigger incision than is necessary for simply removing the target tissue. Moreover, the need to penetrate through relatively thick layers of overlying tissue can complicate identification of the target region, often requiring that larger volumes of tissue be removed to assure to complete removal. Additionally, the ability to cut down into internal organs during minimally invasive endoscopic procedures is significantly more limited than in open surgical procedures.
Surgical instruments for removing tissue beneath a tissue surface have been developed. For example, instruments employing specialized cutting blades for chopping or "morcellating" tissue into small pieces and aspirating the resulting debris have been developed. While such instruments are at least theoretically capable of being manipulated to remove a defined volume of tissue beneath a tissue surface, their performance suffers in various ways. Most importantly, tissue morcellation can result in significant bleeding which is difficult to staunch. Thus, these techniques would not be useful in highly vascularized tissues, such as many muscle and organ tissues. Even when combined with electrosurgical coagulation, such tissue morcellation devices are probably not useful for the removal of large tissue volumes beneath a tissue surface where bleeding control is problematic.
For all of these reasons, it would be desirable to provide improved apparatuses and methods for tissue removal beneath tissue surfaces. In particular, the devices and methods should be suitable for use in minimally invasive procedures, such as procedures where the devices are introduced through a port and viewed under endoscopic viewing. The methods and devices should further allow access to a target tissue region with minimum disruption and damage to the overlying "non-target" tissue. Additionally, it would be desirable to provide tissue removal regions with a simplified approach for removing the debris resulting from the tissue removal. It would be particularly desirable to provide such tissue removal methods and devices which result in minimum or easily controlled bleeding at the tissue removal site. Such methods and apparatuses should still further provide for removal of controlled volumes, even relatively large volumes of at least 0.5 cm.sup.3, preferably at least 50 cm.sup.3, and still more preferably at least 500 cm.sup.3, or more. The methods and apparatuses should also be useful on a wide variety of tissue types and for a wide variety of specific procedures. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
A loop electrode for radiofrequency electrosurgical excision of a tissue volume in solid tissue is described in Lorentzen et al. (1996) Min. Invas. Ther. & Allied Tecnol. 5:511-516.
Three-dimensional electrode arrays for deployment in solid tissue followed by the application of radiofrequency energy to necrose tissue volumes are described in U.S. Pat. Nos. 5,827,276; 5,735,847; and 5,728,143.
Atherectomy catheters having radially expansible blade structures intended for rotational stenotic excision in blood vessels are described in U.S. Pat. Nos. 5,556,408; 5,554,163; 5,527,326; 5,318,576; 5,100,423; and 5,030,201. In particular, U.S. Pat. No. 5,554,163, describes a catheter having a flexible "cutting" element that may be radially deployed from the catheter body. U.S. Pat. No. 5,100,423, describes a cutting structure comprising a plurality of helically-shaped cutting wires that can be connected to an electrosurgical power supply to effect cutting of obstructing matter in a blood vessel. The following patents describe other electrosurgical instruments: U.S. Pat. Nos. 2,022,065; 4,660,571; 5,217,458; 5,578,007; 5,702,390; 5,715,817; 5,730,704; 5,738,683; and 5,782,828.